Generally, electrospinning is used to produce a fine diameter fiber by extruding a source liquid for fiber charged with a voltage.
Electrospinning traces its roots to electrostatic spraying, in which when a water droplet forming on the tip of a capillary tube because of the water surface tension is charged with a high voltage, a fine diameter filament erupts from the surface of the droplet.
Electrospinning is based on the phenomenon wherein when an electrostatic force is applied to a polymer solution or a polymer melt having a sufficiently high viscosity, the solution or the melt forms a fiber. Because the electrospinning can produce fine diameter fibers from a source liquid for fiber, electrospinning is in recent years being used to produce nanofibers the diameters of which are on the scale of from several nanometers to several hundred nanometers.
Compared to conventional superfine fibers, nanofibers intrinsically have a high surface to volume ratio and a variety of surface and structural characteristics and, accordingly, the nanofibers are used as essential materials for high-technology industries, such as the electrical, electronic, environmental and biotechnology industries, and the application of the nanofibers is expanding to include their use as filters in the environmental industry, materials for the electrical and electronic industries, medical biomaterials, etc.
Nanofibers are typically produced using an electrospinning injection nozzle which extrudes a source liquid for fiber using air.
The electrospinning injection nozzle includes: a source liquid extruding unit that is formed in a spinneret body and extrudes the source liquid for fiber; and
an air nozzle unit formed around the source liquid extruding unit in the spinneret body and having an air injection hole extending downwards from the periphery of the source liquid extruding unit, wherein the source liquid for fiber extruded from the source liquid to extruding unit is injected together with compressed air that has been fed downwards from the periphery of the source liquid extruding unit through the air injection hole.
An electrospinning device also includes a collector that collects the fiber drawn from the electrospinning injection nozzle.
In an electrospinning device, the electrospinning injection nozzle is connected to the positive pole and the collector is connected to the negative pole so that a voltage difference is created between the nozzle and the collector which renders electrospinning possible.
The electrospinning nozzle can produce nanofibers that have a diameter on the scale of from several nanometers to several hundred nanometers by injecting the source liquid for fiber together with the compressed air.
In the conventional electrospinning nozzle, to realize effective injection, the end of the source liquid extruding unit is recessed into the air injection hole.
However, when the conventional electrospinning nozzle is used to carry out general electrospinning in which only the source liquid for fiber is injected, the fiber formed by injecting the source liquid for fiber may be caught by the air injection hole and may clog the air injection hole. Accordingly, the conventional electrospinning nozzle is problematic in that its issue is limited to producing only nanofibers with diameters ranging from several to several hundred nanometers by injecting high-compressed air.
Further, another electrospinning nozzle in which the end of the source liquid extruding unit protrudes outside the air injection hole has been proposed.
However, in this electrospinning nozzle, to realize error-free electrospinning, the protruding length of the source liquid extruding unit is limited to 1˜3 mm. Due to the limited protruding length, this electrospinning nozzle cannot carry out pure electrospinning in which only the source liquid for fiber is injected without injecting air.
In other words, in the related art, a pure electrospinning nozzle that carries out to pure electrospinning by injecting only the source liquid for fiber and an air electrospinning nozzle that carries out air electrospinning by feeding air have been separately produced and separately used.
Therefore, when the electrospinning device is used to produce a product having a variety of structural layers made of different diameter fibers using both the pure electrospinning nozzle carrying out the pure electrospinning by injecting only the source liquid for fiber and the electrospinning nozzle that carries out air electrospinning by feeding air, it is necessary to separately use the two types of electrospinning nozzles and this increases the facility cost and requires the nozzle to be frequently changed between the two types of electrospinning nozzles during an electrospinning process.
Furthermore, in the conventional electrospinning nozzle, an electrode is directly connected to the spinneret body and allows an electric current to flow in the source liquid for fiber fed into the source liquid extruding unit, so that the magnetic field may leak from the spinneret body to the outside. Accordingly, the conventional electrospinning nozzle is problematic in that the nozzle may not carry out stable or effective electrospinning and it is required to apply a high voltage so as to compensate for the leakage of the magnetic field.
Another problem of the conventional electrospinning nozzle resides in that to realize a direct connection of the electrode, it is required to use a metal material which is a conductive material to make the nozzle, and accordingly the nozzle is heavy and the production cost thereof is increased.